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Thanks!

 Feb 22, 2018
edited by Guest  Feb 22, 2018
 #1
avatar+128079 
+1

Due to symmetry  the x coordinate of the vertex = 5

 

The points  (3,0) (7,0) and (2, - 5)  are on the graph

 

And we have this form

 

y  =  ax^2 + bx + c

 

The x coordinate of the vertex  =  

 

-b / (2a)  =  5

-b  = 10a

b  =  -10a

 

So we have that using  (3,0)

 

0  =  a(3)^2 - 10a(3)  + c

0 =  9a - 30a + c

0  =  - 21a + c

-c = -21a

c = 21a

 

And using  (2, -5)

-5  =  a(2)^2  - 10a(2) + 21a

-5  = 4a - 20a + 21a

-5  = 5a

a  =  -1

 

And b =  -10(-1)  =  10

And c = 21(-1)  = -21

 

So our function is :

 

y = -1x^2 + 10x  - 21

 

Here;s the graph : https://www.desmos.com/calculator/u2qnb8dswx

 

 

cool cool cool

 Feb 22, 2018
 #2
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0

Thanks so much!

Guest Feb 22, 2018

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